Can't scale, what's wrong?
Blender 2.91 Update: Click on Options in the upper right hand of your viewport. Under Transform &gt; Affect Only, uncheck Locations.
Refer to image below:

This can also be accessed by hovering over viewport and pressing N &gt; Click the Tool tab&gt;Reveal Options&gt;Reveal Transform&gt;Uncheck Affect Only property Locations.
Refer to image below:


Previous answer from 2015:
Oops. I had things locked with Manipulate Center Points.